It has been known for many years to provide for the controlled release of various substances ranging from inks to pesticides to fragrances, by encapsulating the desired substance in a matrix or shell of another material, such as a polymer, which is later disintegrated to release the desired substance, either by dissolving the encapsulating material slowly in the environment or by rupturing the encapsulating material by friction or other force during application or use of the substance. As a result, the encapsulated substance is protected during shipping, storing, handling, and sometimes even during application, so that the substance may be released in a slow or controlled manner.
Various methods are also known for encapsulating substances for controlled release. Probably the most commonly used techniques are spray drying and coacervation. In both of these methods a polymeric or similar matrix material, such as a gum, gelatin or porous cellular material, must be provided to contain or incorporate the substance desired to be released. Generally, this encapsulating material is an inert, biodegradable substance, since it will serve no useful purpose after the controlled release is completed.
The patent literature is replete with examples of encapsulated materials, particularly fragrances, perfumes, flavoring agents, pharmaceuticals and cosmetics, including antiperspirants and deodorants. However, in each case, it is necessary to use an extraneous material as at least a part of the encapsulating agent, and applicants are not aware of the prior use of the primary active ingredient as the sole encapsulating agent without the necessity of using extraneous materials to form the encapsulating shell.
For example, U.S. Pat. Nos. 3,886,125 and 3,966,902 of Chromecek disclose the use of polymer complexes containing aluminum, zinc or zirconium metal in complex bound form for entrapping active agents such as medicaments, fragrances, pesticides, antibacterials and like substances. While the aluminum, zinc or zirconium compounds used in the polymer complexes may be ones which have antiperspirant activity, no claims of such activity are made for the complexes, and these metal complex structures are used to inhibit the gelling of the reaction system which requires the polymerization of an organic monomer to form the encapsulating material. Moreover, Chromecek contemplates encapsulating an antiperspirant active aluminum complex within the polymer complex.
U.S. Pat. No. 3,091,567 of Wurzburg, et al. describes a method of emulsifying a flavoring oil or perfume in a solution containing an aluminum sulfate starch derivative. The emulsion is then spray dried to yield free-flowing particles which permit a gradual release of the perfume encapsulated in the particles. While the polyvalent metal salts used to form the starch derivatives may include salts used as antiperspirant actives, no antiperspirant activity is attributed to the derivatives, and the derivatives form water-repellent films.
U.S. Pat. No. 3,691,271 of Charle, et al. discloses the encapsulation of a deodorant within a particle shell such as gelatin, cellulose or polyvinyl alcohol. The deodorant is released as perspiration dissolves or permeates the particle shell. No antiperspirant activity is disclosed or claimed.
U.S. Pat. No. 4,579,779 of Ohno describes a method of encapsulating organic liquids such as fragrances in hollow particles of silica, while U.S. Pat. No. 3,201,353 of Corben describes a method for encapsulating a water-immiscible material within a gelatin complex containing a water-soluble zirconyl salt. The water-immiscible liquid may be a flavoring agent or pharmaceutical, for example.
U.S. Pat. Nos. 4,605,554; 4,364,515 and 4,278,206 of AE Development Corporation describe hydrophobic metal oxides which may contain an antiperspirant or similar material which encapsulates discrete water globules which are released when the metal oxide particles are subjected to high shear mixing, such as during roll-on application of the antiperspirant product.